1. Technical Field
This invention relates generally to a method for forming a structure suitable for use as a core member, either by itself or as part of a multi-ply panel, and more particularly to a continuous method for forming such a structure having a plurality of elongated passageways disposed parallel to the thickness of the structure.
2. History of Related Art
Many structural arrangements have been proposed for use as a core member in laminated assemblies such as multi-ply panels having a surface ply bonded to at least one side of the core member. In particular, core structures formed of short elongated tubular segments arranged in parallel to the thickness of the core member have been found to provide exceptional resistance to compressive deformation and crush damage. However, because such structures comprise very large numbers of separate tubes or similar cell components, they have heretofore been difficult to assemble and manufacture economically. For example, U.S. Pat. No. 5,032,208, issued Jul. 16, 1991 to Horst Strauss describes a process for manufacturing a bundle of tubes by loading the tubes into a gutter having a moveable end wall. The end wall is then moved incrementally to expose one end of the tubes, which are then cut and the cut ends fused whereby adjacent disposed tube ends are joined together. The bundle is then moved to a position whereat a second cut can be made, then moved to a position at which a third cut can be made, and continued, seriatim, until the entire bundle has been cut into the desired number of cores. The Strauss process is not only cumbersome, allowing only one transverse cut and fusing operation at a time, but also is dependent upon precise, controlled movement of one end of the gutter while maintaining a desired alignment of the uncut tubes in the bundle.
In an earlier arrangement, a structural core panel construction is described in U.S. Pat. No. 2,477,852, issued Aug. 2, 1949 to C. E. Bacon, in which short tubular members are adhesively joined along their entire length. Alternatively, other shapes, such as corrugated strips may be precisely aligned and adhesively joined together along mating corrugations and then transversely cut to provide a core. In all of the arrangements taught in the Bacon structure, the individual components are adhesively joined along their entire length. This process is also cumbersome and time consuming, requiring that the adhesive be set before moving the structure for subsequent processing, such as applying a cover to the core member.
Recently, U.S. patent application Ser. No. 5,683,782 issued Nov. 4, 1997 to Rainer Duchene describes a process for producing a honeycomb structure in which the individual components of the structure are coated with a heat-activated adhesive prior to assembly. After assembly, the adhesive is activated by a thermal treatment in which the individual components are bonded along their entire length. Thus, the Duchene process requires a precoating step prior to assembly and a separate thermal treatment prior to subsequent processing.
The present invention is directed to overcoming the problems set forth above. It is desirable to have a continuous method for forming a structure suitable for use as a core, instead of the above-described batch manufacturing processes. It is also desirable to have a method for forming a structure suitable for use in which a plurality of cores may be formed by simultaneous multiple cuts of a pre-assembled stack, or bundle, of components having internal passageways. It is also desirable to have such a structure that does not require adhesive joining of the separate components prior to forming into a core member. Furthermore, it is desirable to have a method by which a structure suitable for use as a core member can be formed without requiring a fixture having a moveable end wall by which only a single core member is formed before requiring movement of the assembled tubes to a subsequent position at which another core may be formed. Moreover, it is desirable to have a method for forming a plurality of cores simultaneously by which only selected open ends of the elongated members forming the core are fused together.